Preloaded contact system for electric timekeeping device



I Oct. 20, 1970 I J. 0. LE VAN 3,534,5 6

PRELOADED CONTACT SYSTEM FOR ELECTRIC TIMEKEEPING DEVICE Filed out. 1, 1968 3 sheets-sheen v INVENTOR 76 James O LE'VGn -.rlc l T C ATTORNEYS Oct. 20, 1970 T I J. 6. LE VAN 3,534,546

PRELOADED CONTACT SYSTEM FOR ELECTRIC TIMEKEEPING DEVICE Y Filed Oct. 1, 1968 I I :s Sheets-Sheet 2 i106 mvsumn .Jq m gs 0. LeVdn ATTORNEYS J. 0'. LE VAN PRELOADED CONTACT SYSTEM FOR ELECTRIC TIMEKEEPING DEVICE Filed. Oct. 1,1968

' s sheets-sheet s I INVENTOR -Jomes 0.LeVdn 3,534,546 PRELOADED CONTACT SYSTEM FOR ELECTRIC TIMEKEEPING DEVICE James 0. Le Van, Lancaster, Pa., assignor to The Hamilton Watch Company, Lancaster, Pa., a corporation of Pennsylvania Filed Oct. 1, 1968, Ser. No. 764,266 Int. Cl. G04c 3/04 US. Cl. 5828 10 Claims ABSTRACT OF THE DISCLOSURE There is disclosed herein an improved contact system for electric timekeeping devices of the hairspring regulated balance wheel type. The contact system includes a spring loaded movable contact member mounted on the balance wheel and a separate fixed contact member. The movable contact member is displaced relative to the moving balance wheel due to engagement with the fixed contact member but is so constructed that the reaction force between the contacts is essentially uniform whenever the two are engaged. The spring loading and uniform reaction force. is provided by an elongated loop spring secured to the movable contact member and engaged with a curved surface of a mounting pin securing the moving contact member to the balance wheel.

. The present invention relates to an improved contact system for electrical timepieces, and more particularly to a contact system having fixed and moving contact members in which the reaction force between the members is essentially uniform whenever the two contact members are engaged.

Numerous electrical timekeeping devices, including battery operated watches, are known and are commercially available. Among the most satisfactory are those having a hairspring regulated balance wheel driven by the interaction of a magnetic field and a current carrying drive coil. An example of such a device may be found in the electric wrist watch shown in the present assignees U.S. Reissue Pat. No. 26,186, reissued Apr. 4, 1967 to John A. Van Horn et al. for Electric Watch.

In timekeeping devices of this type, the drive coil is ordinarily mounted on the balance wheel and is positioned to pass through the magnetic field produced by one or more permanent magnets. An electrical contact system having a first member mounted on the balance wheel and a second member fixed relative to the balance wheel connects the coil to a source of power, e.g., a battery.

In the case of Wrist watches or the like, small size and low-power requirements are essential to permit the use of small batteries having a relatively long lifetime thereby avoiding the inconvenience of frequent replacement.

One way in which power is conserved is by employing a contact system which provides only intermittent energization of the drive coil, i.e., only during those periods .of time that the coil is actually passing through the magnetic field. Then interaction of the current carrying coil and'the magnetic field produces a force applied to the coil which is transmitted to the balance wheel. This serves to sustain balance wheel oscillation with the frequency being determined by the mechanical characteristics of the hairspring balance wheel system. An indexing system converts the oscillation of the balance wheel into unidirectional motion which may then be utilized for timekeeping or other timing purposes in customary fashion.

The movable member of the contact system, i.e., that mounted on the balance wheel, executes an arcuate motion as the balancewheel oscillates and engages tangen- United States Patent tially with the fixed contact members. As will be appreciated, the reaction force between the contact members is tangential to the balance wheel motion and obviously constitutes a retarding force which must be overcome by the balance wheel drive system in sustaining balance wheel oscillation. In order to obtain full benefit of the intermittent energization, the retarding force resulting from contact member reaction forces must be minimized.

This presents conflicting requirements in that certain contact pressure must be maintained between the members if satisfactory electrical operation is to be achieved. The contact pressure must be great enough to assure that essentially no contact resistance is present or the power provided to the coil will be reduced. In addition, uniform pressure immediately upon engagement and throughout the entire period of engagement followed by rapid disengagement are also desirable to prevent arcing and to assure maximum utilization of available power.

In contact systems of the type under consideration, balance wheel motion produces an operation cycle including engagement and disengagement for one direction of balance wheel oscillation, followed by balance wheel reversal, with engagement and disengagement of the contacts during the second half of the oscillation cycle. The second engagement introduces an additional tangential retarding force which should be minimized for eflicient operation. In addition, the contact system may be so arranged that the balance wheel coil is energized every half cycle, i.e., each time the fixed and moving contacts are brought into engagement by balance wheel oscillation. This requires not only low contact force in both directions, but also uniform loading and rapid disengagement in both directions so that operational symmetry is achieved. Currently available contact systems have been somewhat deficient in one or more of the foregoing requirements, especially in the case of maintaining uniform contact pressure and low retarding force for both direc tions of balance wheel oscillation.

The foregoing requirements are met in accordance with the present invention by the provision of a preloaded contact system in which the movable contact yieldingly engages with the fixed contact member as a result of balance wheel oscillation. A substantially constant restoring force is provided to the movable contact by means of a spring biasing arrangement including an elongated loop spring attached to the contact member and engaging with a curved pin which secures the movable contact member to the balance wheel. The construction is such that the movable contact member executes arcuate motion with the balance wheel and also pivots about its own axis fixed relative to the balance wheel when displaced by engagement with the fixed contact member. The restoring force is uniform, independent of the direction in which the movable contact engages with the fixed contact and, equally important, is substantially uniform independent of the degree of displacement of the moving contact member relative to the balance wheel. Thus, uinform contact pressure is obtained during contact in both directions and is found to result in satisfactory levels of tangential retarding force. Such a result is not feasible with ordinary spring loading, i.e., where spring force is a function of displacement.

Accordingly, it is a general object of this invention to provide an improved contact system for an electric timekeeping device. v

It is another general object of this invention to provide an improved contact system for an electric timekeeping device having a relatively low retarding effect on. balance wheel motion.

It is also an object of this invention to provide an improved contaot system as described above providing substantially uniform reaction force between the contact members during the entire period of engagement.

Another object of this invention is to provide an improved contact system as described above characterized by substantially symmetrical operation independent of the direction of balance wheel oscillation.

Yet another object of this invention is to provide an improved contact system for a balance wheel type electric timekeeping device including a fixed contact and a movable contact mounted on a pivot attached to the balance wheel with an elongated loop spring attached to the movable contact and engaging with a curved surface on the pivot to provide uniform reaction force when the contacts are engaged.

It is a further object of this invention to provide an improved contact system for an electric watch in which the movable member is preloaded by an elongated loop spring to provide substantially uniform restoring force during engagement of the contact members.

It is another object of this invention to provide a preloaded contact system in which the moving contact is subjected to a restoring force independent of the magnitude and the direction of contact engagement.

The exact nature of this invention as well as other objects and advantages thereof will become apparent from consideration of the following detailed description and the accompanying drawing in which:

FIG. 1 is an elevational view, face side down, partially in section, showing a portion of the watch mechanism including a balance wheel and hairspring, an indexing mehcanism, and the improved preloaded contact system of this invention;

FIG. 2 is a back view showing the balance wheel and the movable portion of the contact system of this invention;

FIG. 3 is a fragmentary bottom view (i.e., face side up of FIG, 2 showing the movable contact member and its connection to the balance wheel drive coil;

FIG. 4 is an enlarged back view of the completely assembled movable contact member removed from the balance wheel.

FIGS. 5a and 5b are fragmentary views showing operation of the moving contact assembly;

FIG. 6 is a view from the back of the watch showing the construction of the contact cock and fixed contact member;

, FIG. 7 is an enlarged fragmentary view of FIG. 6 showing the construction of the fixed contact and the attached electrically conducting wires; and

FIG. 8 is an exploded view, face side down, illustrating the construction and manner of assembly of the entire preloaded contact system in accordance with this invention.

In FIGS. 1 and 2 there may be seen the overall arrangement of a contact system and other associated portions of an electric timepiece in accordance with this invention. The contact system, generally denoted at 10, includes a moving member 12 and a fixed member 14. Moving contact member 12 is directly mounted on a balance wheel 16, for example, by means of a D-shaped retaining pin 18 as explained more fully hereinafter. Fixed contact member 14, on the other hand, is rigidly secured to a fixed portion of the timepiece movement, e.g., by one or more screws 20 directly to a pillar plate 22, a fragment of which is visible in FIG. 1.

Any balance wheel construction suitable for use in an electric timekeeping device may .be employed with the present invention. One such balance wheel which is particularly suitable due to its low susceptibility to eddy current losses, is shown and described in detail in assignees copending US. patent application Ser. No. 764,172 filed concurrently herewith in the name of John L. Klinck, and entitled Improved Composite Balance Wheel Construction for Electric Timekeeping Devices, the disclosure of which is fully incorporated by reference herein. Since balance wheel 16 is the subject of the aforementioned application, a complete description will not be presented herein. However, those features which are significant in connection with the present invention may be understood from the following brief description in connection with FIGS. 1 and 2.

Balance wheel 16 includes a rim portion 24 and an arm 26 consisting of three radial branches or spokes 28, 30 and 32. A drive coil 34 cooperates with one or more fixed magnets, such as magnet 35, to sustain balance wheel oscillation. Coil 34 is attached to balance wheel 16, as by a pair of mounting tabs 36 and 38 projecting from spokes 30 and 32 of balance wheel arm 26.

As explained in the aforementioned Klinck application, balance wheel rim 24 is a composite structure formed of a coil of fine insulated wire coated with a liquid resinous binder, such as epoxy, and then hardened into a flat ring as shown by curing the binder. A unitary structure of rim 24 and arm 26 is formed by embedding the arm into the rim while the latter is being wound, e.g., by means of three small tabs 40 projecting radially from the ends of arm branches 28, 30, and 32. As shown in FIG. 1, the portions of branches 28, 30 and 32 adjacent tabs 40 are downwardly offset so that the tabs are firmly secured in the body of rim 24. The portion of rim 24 between branches 30 and 32 is cut away as shown in FIG. 2 to allow positioning of drive coil 34 at the desired location.

The construction just described has numerous advantages, but it should be understood that any other suitable balance wheel, e.g., as shown in the aforementioned Van Horn et a1. reissue patent, may be substituted.

Referring still to FIGS. 1 and 2, balance wheel 16 is mounted on a balance staff 42, having its ends 44 and 46 supported conventionally within the watch. An indexing mechanism, generally denoted at 48 and a hairspring 50 are also mounted on balance staff 42. As best illustrated in FIGS. 1 and 3, indexing mechanism 48 includes a drive roller 52 with a jewel roller pin 54 depending upwardly from roller 52 toward the face side of the watch. A saefty roller 56, having crescent shaped cut out 58 forms the top portion of the indexing mechanism and may be formed integrally with drive roller 52 as shown, or in separate parts, both press fitted onto the face end of balance staff 42.

In customary fashion, roller pin 54 engages with the forked end of a pallet 59, a fragment of which is shown in FIG. 1. A conventional guard pin 60 engages with safety roller 56 to prevent overbanking as balance wheel assembly 16 oscillates.

Hairspring 50 is positioned at the back end of balance Wheel assembly 16. The hairspring is attached at its inner end to a collar 62 press-fitted onto balance staff 42, and

at its outer end to a conventionally positioned anchor stud 64. The construction and operation of the above described portionsof the electric Watch mechanism are entirely conventional, and further description thereof is omitted in the interest of brevity.

The construction and assembly of the preloaded contact system of this invention will now be described in detail. As previously mentioned, contact system 10 includes a moving portion 12 constituting a part of the balance wheel assembly and a fixed portion 14. As best illustrated in FIGS. 1, 6, and 7, fixed contact assembly 14 is comprised of a contact support plate 66 including a plurality of adjustable mounting slots 67 and carrying a pair of electrical terminal posts 68 and 70 and a fixed electrical contact member 72.

Terminal posts 68 and 70 are adbesively secured in apertures in the plate by epoxy or other electrically insulating resin. The posts. extend through the plate and depend downwardly as shown in FIG. 1, toward the face side of the watch. Conductive clips 74 and 76 are attached to posts 68 and 70 and provide electrical connections to the battery.

Electrical contactmember 72 is formed of awedgeshaped jewel body 78 pressfitted into an aperture in plate 66. Metallic contact plates 80 and 82 are attached to tapered faces 84 and 86 respectively of jewel body 78. This may be accomplished by welding the contact plates to metallized surfaces deposited on tapered faces 84 and 86, or in any other suitable fashion.

For the embodiment illustrated and described herein energization for drive coil 34 is intended to be accomplished twice for each cycle of balance wheel oscillation. Under such circumstances, it will be appreciated that the motion of the coil 34 through the magnetic field will be in opposite directions for successive current pulses. Thus, the energizing arrangement must be such that the force coupled to the balance wheel is in a direction that will aid rather than retard the balance wheel motion.

One way to accomplish this is by providing a fixed polarity current pulse to the coil at such points in the balance wheel cycle that the sense of the magnetic field is opposite for each successive current pulse. For example, with fixed polarity current, three magnets may be provided, the center and one adjacent magnet providing a north-south field and the center and the other adjacent magnet providing a south-north field. The coil may then be energized at such time that it interacts with the northsouth field when traveling in one direction, and with the south-north field when traveling in the other direction. Alternatively, two magnets providing a fixed sense magnetic field can be employed if the current ulse is provided with opposite polarity for each half cycle of balance wheel motion.

The latter approach has been employed in the present case. Thus, it is necessary that opposite current polarities be provided when the moving contact portion engages surfaces 80 and 82, respectively, of fixed contact member 72. To this end, a first wire 87 is connected in any suitable fashion, as by soldering or welding, between contact surface 80 and associated terminal post 68, as shown in FIGS. 1 and 6. Likewise, a second wire 88 is connected between contact surface 82 and terminal post 70. Conducting clips 74 and 76 are coupled to positive and negative sides of the power supply battery while the watch casing itself is maintained at a neutral ground.

Contact surfaces 80 and 82 are electrically isolated from each other and from support plate 66 (which is at neutral potential by the insulating jewel body 78 of contact member 72 and by the vertical spacing of th contact surfaces from the support plate as illustrated in FIG. 7.)

As a result, when the moving contact engages with the contact surface on one side of the fixed contact member 72, it is energized with current of one polarity but when it engages the contact surface 82 on the opposite surface of the fixed contact member during the second half of the balance wheel oscillation cycle, it is energized by current of the opposite polarity. This assures that the energizing pulse will aid rather than retard balance wheel motion.

As best illustrated in FIGS. 1 through 4 and 8, moving contact assembly 12 includes a first contact subassembly 90 comprised of a contact support plate 92 and a finger contact 94. Cooperating with first' ontact subassembly 90 is a second contact subassembly 9.6 including a circuit continuity spring 98, and a contact place 100 by which electrical energy is transferred to balance wheel drive coil 34.

First and second contact subassemblies 90 and 96 are both mounted on balance wheel assembly 16 by means of D-shaped retaining pin 18. Second contact subassembly 96 if fixed relative to the balance wheel by a press fit of retaining pin 18 in a complementary D-shaped opening 102 in contact plate 100. However, first contact subassembly 90 is movably mounted relative to the balance wheel. This is accomplished by provision of an enlarged bucket-shaped opening 104 in support plate 92. An elongated loop spring 106 cooperates with retaining pin 18 and with first contact subassembly 90- as described hereinafter to secure the latter in place and to provide the constant contactreaction force between the fixed and movable portions 12 and 14. A finger cap 108 receives D- shaped pin 18 with a press fit in a D-shaped opening 110 and serves to retain first contact subassembly against axial movement.

First contact subassembly support plate 92 includes a central portion 112, a short arm 114, and a diametrically opposite long arm 116. Short arm 114 includes flat vertical edge 114 to which finger contact 94 is attached, as by welding, or in any other suitable manner to provide electrical continuity.

Finger contact 94 is a metal block as shown with a pair of bevelled faces 120 and 122 terminated in a slightly rounded apex 123. Bevelled faces 120 and 122 engage with fixed contact portion 72 as explained hereinafter.

Long arm 116 serves as the connection between first and second contact subassemblies 90 and 96. Electrical connection is made through end 124 of arm 116 which is bent as illustrated in FIGS. 1 and 8 to extend into the plane of continuity spring 98, and engages with hooked end 125 of the spring.

Depending from central portion 112 of first contact subassembly support plate 92 toward the backside of the watch is diametrical rib 126 which cooperates with loop spring 106 to secure first contact subassembly 90 in position. An elongated fiat vertical surface 128 on rib 126 adjacent longer arm 116 (see FIGS. 1 and 8) supports load spring 106 and is permanently secured to the inner surface 130 of the spring by welding. As best illustrated in FIGS. 1 and 4, rib 126 is received within the bight 132 of loop spring 106, the latter being stretched sufiiciently to accommodate D-shaped pin 118 which is received in bucket-shaped cutout 104 when the contact system is assembled.

The complete assembly of moving contact portion 12 is best illustrated in FIGS. 1 through 4. As shown, D-

shaped pin 18 provides an axis for the entire structure. The portions fixed relative to the balance wheel 16, viz. second contact subassembly 96 and finger cap 108, are press fitted onto the balance wheel, e.g., on a small semicircular protrusion 134 of spoke 32 of balance wheel arm 26.

The moving portion of contact assembly 12, i.e., first contact subassembly 90, is secured to D-shaped pin 18 by loop spring 106 and rib 126 as previously explained and is retained against axial movement by the press fit of D- shaped pin 18 into D-shaped opening 102 of contact plate and D-shaped opening of finger cap 108.

The fixed and moving portions are connected -by circuit continuity spring 98 which is movable relative to D-shaped pin 18 and balance wheel 16 in the sense that movement of the balance wheel causes the spring to be wound and unwound during successive half cycles of balance wheel operation. The fiat inner end 136 of spring 98 is welded or otherwise secured to a corresponding vertical flat surface 138 of contact plate 100. The outer end of circuit continuity spring 98 is bent as shown in FIG. 8 and looped about upwardly projecting end 124 of support plate arm 116 and secured as by welding. This provides both mechanical and electrical coupling between the first and second contact subassemblies 90 and 96.

The electrical conduction path from fixed contact member 72 is provided through finger contact 94, arms 114 and 116 and body portion 112 of contact support plate 92, circuit continuity spring 98 and contact plate 100. From the latter, current is supplied to drive coil 34 as shown in FIG. 3 through wire 142 connected between the coil and an elongated terminal 44 of contact plate 100. An arm portion 146 connects terminal 44 with contact plate 100. As shown in FIG. 8, arm 146 is to downwardly olfset to permit clearance of connecting spring 98 upon assembly.

The entire moving contact assembly 12 is electrically isolated from balance wheel 16 which is at neutral or ground potential by the insulating properties of jewel pinv 7 18 and by a flat insulating washer 148 (see FIG. 1) positioned on D-shaped pin 18 between balance wheel arm 32 and contact plate 100.

As will be appreciated from the foregoing and from the assembly as illustrated in FIG. 1, proper operation in accordance with this invention requires that first contact subassembly 90 be free to move in relationship to D- shaped pin 18 and second contact subassembly 96. This is accomplished by making bucket shaped opening 104 oversized in all dimensions relative to D-shaped pin 18. When assembled, vertical wall 150 of D-shaped opening 104 supports the flat surface 152 of D-shaped pin 18 and is sufliciently wide so that corners 154 and 156 of the cutout are free to pivot about vertical edges 158 and 160 of D-shaped pin 18 as illustrated in FIGS. 5a and 5b, and as described more fully hereinafter. Further to facilitate the relative motion, the upper surfaces of finger cap 108 and or rib portion 126 on first contact subassembly 90 are of convex configuration to reduce friction between the moving surfaces (see FIG. 1). The operation of the above-described mechanism may best 'be appreciated from the following description with reference to FIGS. 1, 4, 5a and 5b.

As balance wheel assembly 16 oscillates about balance staff 42, movable contact assembly 12 describes an arcuate oscillatory motion along with the balance wheel itself. The arcuate motion results in finger contact 94 engaging with fixed contact portion 72 in fixed contact assembly 14. Assuming that balance wheel motion is such that finger contact 94 is approaching fixed contact portion 72 from the side facing contact surface 82, as illustrated in FIG. 1, engagement of the contact members causes a reaction force having a component tangential to the direction of balance wheel motion between beveled point 120 of finger contact 94 and fixed contact surface 82. A like tangential force in the opposite direction also arises when moving finger contact 94 engages the opposite side of fixed contact portion 72, i.e., contact surface 80. In accordance with this invention, these tangential forces, which constitute retarding forces for balance wheel oscillation, are minimized by virtue of the interaction of the elongated loop spring 106 and curved face 162 of D-shaped pin 18'.

Specifically, since face 162 of D-shaped pin 18 is curved, since the point of interaction with loop spring 106 is substantially radially aligned with finger contact 94, and further since the total distance between the point of interaction and the vertical edges 158 and 160 of pin 18 is small, the tangential reaction-which derives from the restoring torque about pin 18 will always be quite small, and essentially independent of rotation of first contact subassembly 90 relative to the pin. Whether contact subassembly 90 is in the extreme positions shown in FIGS. 5a and 5b, orat some intermediate position, the force between contacts 72 and 94 is small and essentially unchanged. The tangential component due to friction between pin 18 and spring 106 is also relatively small so that movement of the spring around the pin itself does not produce substantial retarding force.

Thus, immediately upon engagement of fixed contact portion 72 and finger contact 94, the reaction force'is established. This force remains substantially constant, independent of the direction of movement of finger contact 94 from the time the fixed and moving contacts engage until the movement of balance wheel 16 causes finger contact 94 to move beyond fixed contact portion 72. Upon disengagement, the restoring force of spring 106 causes first contact subassembly 90 to return to its rest position, i.e., with flat surface 152 resting against surface 15 of bucket-shaped opening 104.

Whenever fixed contact 72 and moving contact finger 94 are engaged, circuit continuity spring 98 will be wound or unwound, depending on the direction of motion relative to the fixed contact portion 72. The energy stored in spring 98 does cause a variation in the contact pressure between finger contact 94 and fixed contact 72,

but it is found that this variation is minimal, i.e., less than about 10% and may be disregarded.

The arrangement shown, therefore, provides a convenient and reliable mechanism for coupling the drive coil current from fixed contact portion 72 notwithstanding the motionof the first contact subassembly relative to the balance wheel and the drive coil. As mentioned, this is true regardless of the direction of contact engagement.

While the foregoing represents the preferred embodiment of the invention described, it should be appreciated that various modifications may be made without departure from the invention disclosed. For example, the preloaded contact arrangement may be used to advantage whether drive coil 34 is to be energized wiith like or opposite polarities during each oscillation half-cycle. In such an arrangement, fixed contact portion 72 will be provided. current of only a single polarity for both contact faces. Force reversal may then be achieved by use of three magnets providing a magnetic field of opposite sense for alternate half cycles as previously explained.

Alternatively, the principles of the present invention may be applied to an electric watch construction in which energization is provided only once per cycle. In such an arrangement, only one contact face of fixed contact portion 72 would be utilized.

Various other structural modifications are also contemplated, particularly including variations in the shape of the various elements constituting the contact system and its subassemblies.

Thus, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. An electric watch having a power source, a balance wheel, a drive coil driving said balance wheel, and a source of magnetic flux, and a contact system for intermittently energizing said coil, said contact system comprising: a fixed contact assembly mounted in said watch, and a moving contact assembly mounted on said balance wheel, said moving contact assembly being comprised of a first subassembly and a second subassembly; means for attaching said first and second subassemblies to said balance wheel, with said first subassembly being movably mounted relative to said balance wheel and said second subassembly being fixedly mounted relative to said balance wheel; said moving contact assembly including means for electrically connecting said first and second contact subassemblies; said fixed contact assembly having a contact portion adapted to be connected to said power supply for said watch, said first contact subassembly of said moving contact assembly having a finger contact for intermittently engaging said contact portion on said fixed contact assembly as said balance wheel oscillates; said mounting means for said first and second contact subassemblies being operative to maintain a substantially constant contact force between said fixed contact portion and said finger contact during the entire period of contact engagement.

2. An electric watch as defined in claim 1 wherein said means for attaching said first and second contact subassemblies to said balance wheel includes an elongated pin attached to said balance wheel, said pin having a curved surface and an opposed flat surface; wherein said first contact subassembly includes a support portion carrying said finger contact mounted thereon, and having an aperture for receiving said pin, said aperture having a flat surface for engagement with the corresponding surface of said pin and being oversized relative to said pin to permit movement of said first contact subassembly around said pin when said finger contact engages said fixed contact portion; and an elongated endless loop spring attached to said support portion, said spring receiving said pin within the bight thereof and engaging said curved surface of said pin to retain said flat surface of said aperture in contact with said flat surface of said pin when said finger contact and said fixed contact por tion are not engaged.

3. An electric watch as defined in claim 2 wherein said second contact subassembly is comprised of a plate member fixedly mounted on said pin out of the plane of said first contact subassembly projecting into the plane in the plane of said plate member, the inner end of said spiral spring being secured to said plate member and the outer end of said spiral spring being secured to a portion of said first contact subassembly projecting into the plane of said spiral spring, said plate member including a portion adapted to be electrically connected to the drive coil of said watch.

4. An electric watch as defined in claim 1 wherein said finger contact is electrically connected through said first contact subassembly and said second contact subassembly to said drive coil; wherein said fixed contact portion comprises a body of insulating material, first and second electrically isolated conducting surfaces on said body; and means for connecting said first and second surfaces to opposite polarity terminals of said power supply; and wherein said finger contact is positioned to engage said first contact surface as said balance wheel moves in one direction and to engage said second contact surface as said balance wheel moves in the opposite direction; whereby said coil is energized with opposite polarities for each half cycle of balance wheel oscillation.

5. An electric watch as defined in claim 1 wherein said means for attaching said first and second contact subassemblies to said balance wheel comprises a jewel pin having a generally D-shaped cross section, one end of said jewel pin being fixedly secured to said balance Wheel; wherein said second contact subassembly is fixedly mounted on said jewel pin in spaced proximity to said balance wheel; wherein said first contact subassembly is movably mounted on said D-shaped pin; and wherein said attaching means further includes an elongated endless loop spring secured to said first contact subassembly and receiving said D-shaped pin within the bight thereof; said spring engaging with the curved surface of said D-shaped pin whereby, in the absence of external force on said first contact subassembly, said elongated loop spring maintains a fixed positional relationship between said first contact subassembly and said pin.

6. An electric watch as defined in claim 1 wherein said first contact subassembly comprises a generally circular flat body portion having a diametrically disposed rib on one side thereof and a pair of projecting arms diametrically lying in the opposite plane of said body portion and extending in generally perpendicular relationship to said rib portion: Said first arm having said finger contact attached thereto; said second arm including a portion projecting out of the plane of said body portion for attachment to said second contact subassembly.

7. An electric watch as defined in claim 6 wherein said second contact subassembly comprises a generally circular flat body portion, in parallel spaced relation to said body portion of said first contact subassembly, a spiral spring having its inner end attached to the body portion of said second contact subassembly and its outer end attached to said projecting portion of said second arm of said first subassembly, and means coupling the body portion of said second contact subassembly to said drive coil to provide a continuous electrical path between the finger contact of said first contact subassembly and said drive coil.

8. An electric watch as defined in claim 7 wherein said means for attaching said first and second contact subassemblies to said balance wheel comprises an elongated generally D-shaped pin formed of electrically insulated material fixedly secured to said balance wheel, wherein the body portion of said second contact subassembly includes a D-shaped aperture for receiving said pin in a tight-fitting relationship; and wherein said body portion of said first contact subassembly includes a generally bucket-shaped cutout for receiving said D-shaped pin in a freely moving relationship, and an elongated loop spring attached to said rib portion of said first contact subassembly body, said spring receiving said D- shaped pin within the bight thereof and engaging with the curved surface of said pin to maintain a substantially constant reaction force between said first contact subassembly and said pin; and a cap portion fixedly mounted on said pin to restrain said first contact subassembly against axial movement.

9. An electric watch as defined in claim 8 wherein said bucket-shaped cutout includes a flat wall including a portion of said rib, engaging with the flat surface of said D-shaped pin, said fiat wall of said cutout being slightly oversize relative to the flat surface of said pin, the ends of said flat wall being defined by flaring side walls of said bucket shaped cutout merging into a further Wall in generally parallel spaced relation to said flat surface, the spacing between said fiat wall and further wall being substantially greater than one-half the width of the flat surface of said D-shaped pin.

10. An electric watch as defined in claim 9 wherein said elongated loop spring is of flat band-like configuration and wherein said rib portion is received within the bight of said spring with a portion of the inner surface thereof being secured to the side of said rib opposite said flat wall of said cutout.

U..S. Cl. X.R.

UNITED S'IA'IES PATENT OFFICE 56 CERTIFICATE OF CORRECTION Patent No. 3,534,546 Dated October 20, 1970 Invenwfl JAMES 0. LeVAN It is certified that error appears in the above-identified patent: and that said Letters Patent are hereby corrected as shown below:

T Column 3, line 30, "mehcanism" should read mechanism Column 4, 1

line 40, "saefty" should read safety line 50 after "balance" insert staff 42 directly below balance line 69, "adbesively" should read adhesively Column 5, line 47, "th" before "contact" should read the line 62, "place" should read plate --v A .1 Column 8, line 43, after "coil" insert for Column 9, line 13 should read of said first contact subassembly, a spiral spring lying --q" SIGNED m sumo 61971 wmuulmm Edward 1!. Wk loan at We Offiow 

